Implement new block-level documentation diagnostics

[sharwell]

This pull request includes the implementation of three brand-new StyleCop rules, along with code fixes for each. A description of each of these rules can be found on the associated issue:

• Implement new diagnostic SA1653 PlaceTextInParagraphs (fixes Place text in paragraphs #601)
• Implement new diagnostic SA1654 UseChildBlocksConsistently (fixes Use block-level elements consistently #602)
• Implement new diagnostic SA1655 UseChildBlocksConsistentlyAcrossElementsOfTheSameKind (fixes Use block-level elements consistently across elements of the same kind #603)

[sharwell]

I rebased and renumbered these rules to account for SA1652 (EnableXmlDocumentationOutput) which was added in the meantime. I also fixed some warnings which appeared due to new style rules being enforced. 😄

[sharwell]

Some statistics on number of violations:

Project	SA1653	SA1654	SA1655
StyleCopAnalyzers	48	6	9
Roslyn	997	65	6
Code Contracts	60	497	6

[Noryoko]

❓ Should this get wrapped in <para>?

[sharwell]

Yes, as part of SA1654 it would be wrapped in <para> elements, but this test is for SA1655. SA1655 says the documentation for ArgumentException contains blocks, and therefore the documentation for all <exception> elements should be written as blocks. The diagnostic is reported on ArgumentNullException since it contains only inline content.

[Noryoko]

👍

[sharwell]

I'm going to move this to a new project.